Wellington's leaky pipes predicament

BY JIM CHIPP - THE WELLINGTONIAN

Wellingtonians' real water problem is how much leaks out of its ageing pipes, says independent engineer Frank Cook.

Mr Cook made a presentation to Wellington city councillors at a meeting discussing the future of Wellington's water supply.

He showed councillors a map of the city's night-time usage in June this year when, he said, not much lawn sprinkling was likely to be happening.

"One can see the average litres per connection [of likely leakage] is probably between 10 and 14 litres per hour," he said.

The flow rate at that time amounted to more than 25 per cent of Wellington's water consumption and indicated high system leakage. "Spending only $108,000 a year addressing leaks is totally unsatisfactory," he said.

Wellington City Council buys $12 million a year worth of water from Wellington Regional Council, which means that Wellington city could be paying $2.5 million for water that is unaccounted for.

In 2006 a single pipe failure in Newtown over a three-month period leaked more water than the entire storage capacity of the Te Marua storage lakes, said Mr Cook.

The lowest points on the map, where the water pressure is highest, were where the night-time flows were highest, meaning that much of the flow was likely to be leakage, Mr Cook told The Wellingtonian.

A council spokesman cautioned that night-time flows were not completely attributable to leakage, because there were some 24-hour commercial uses, such as the Taylor Preston freezing works at Ngauranga and CBD bars that operated very late at night.

Mr Cook also pointed out to councillors that Wellington City Council had in the past overstated residents' water use, at 350 litres per connection per day, and that although council disputes resolution officer Chris Brown had acknowledged the errors and promised to publicly correct them, this had never happened.

Instead, said Mr Cook, the council had redefined the word "residential".

Mr Brown said the council had subtracted all metered commercial use of water from the gross purchase and attributed the rest, including leakage, to residents to come up with its consumption figure.

Mr Cook also said underlying assumptions of the report were wrong – that there was excessive residential garden watering in summer, and that universal metering could save 15 per cent of water use.

"There is much research on this question of water consumption following the introduction of water meters," he said.

"Where there have been savings from the introduction of water meters, they have largely been where summer use has far exceeded winter use and where leakage has been substantially reduced concurrent with the introduction of the meters."

Wellington City Council environmental portfolio leader Celia Wade-Brown said Wellington could not be compared to other cities, because it had old pipes, hilly terrain and was subject to frequent earthquakes.